The present invention finds applicability and utility, among other uses, as a helium pressure relief valve for semi-conductor manufacturing systems, the latter operating at a temperatures nearing 0 degrees Kelvin.
In particular, a specific pressure relief valve assembly of this invention is utilized to control the system pressure within gas compressors, and is capable of modulating gaseous helium flow over a range of 0-100 scfm with a 20 psi maximum pressure override characteristic. No pressure set point is allowed and 0.50 scfm flow rate is considered crack/reset flow. In addition, the valve must have an adjustable pressure setting and must pass a wrench “tap” test, with this test basically introducing a vibration or instability into the valve assembly, when installed and while modulating flow at 85 scfm.
A known prior art design pressure relief valve assembly is unable to meet the noted pressure override characteristic or stability requirement without the use of an additional, external, separate device, taking the form of a 2 inch diameter by 12 inch long stainless steel surge tank. It is the function of this separate surge tank to dampen the valve assembly operation in order to obtain stable operation thereof. Furthermore, in this prior art construction, the pressure is fixed, thus permitting no such adjustments. In addition, the same prior art construction also utilizes conical elastomeric seals which do not permit precision breakaway at the set point, thus overshooting the pressure setting.